The Kettlebell swing is the foundational lift for kettlebell training. The same goes for kettlebell doubles. The video below shows the double swing and later a simple complex beginning with the swing, one rep of alternate cleans, and finishes up with the clean and jerk.
Swings (single or double) are terrific for developing hip snap and target the glutes and hamstrings. Coaching points include: drive from heels, snap hips, keep back flat (big chest and butt). Weight should float close to eye level from hip drive, with no engagement of shoulders.
Other benefits include: trunk (core strength) and grip strength.